Infectious diseases remain a leading cause of illness and death worldwide, particularly among children. However, today there are relatively few Pediatricians dedicated to investigating fundamental scientific questions relating to infections in children. The Division of Pediatric Infectious Diseases at Yale University is a diverse group of basic scientists and clinical researchers who have made important contributions to our understanding of the pathogenesis and epidemiology of infections in children. For more than 25 years, the Division of Infectious Diseases at Yale has trained motivated Pediatricians for productive careers in research, many of whom have assumed prominent leadership roles in academic medical centers, government agencies, and industry. This application for competing renewal of a Ruth L. Kirschstein Institutional National Research Service (T32) Award, which has been funded since 1980, requests support to train four Physician-Scientists per year in each of the next five years. Physicians will be recruited into the program following completion of Residency training in Pediatrics. The cornerstone of this training program will consist of a closely mentored and intensive training experience in basic science or clinical research related to Pediatric Infectious Diseases. Fellows will choose one;of three research tracks designed to highlight the unique expertise and training capabilities of the Yale faculty mentors: Microbial Pathogenesis, Clinical Epidemiology, and Global Infectious Diseases. Required didactic teaching will be available through Graduate level courses offered by the Yale Combined Program in the Biological and Biomedical Sciences, the School of Epidemiology &Public Health, the Robert Wood Johnson Clinical Scholars Program, and the Yale Investigative Medicine Program, with opportunities for trainees to receive advanced degrees, including the Master's in Public Health and the PhD. Fellows will also receive clinical training leading to eligibility for board certification in Pediatric Infectious Diseases, as well as individualized mentoring in career development. It is a primary objective of this program to train Pediatric specialists for successful research careers, with the ultimate goal of alleviating the devastating impact of infectious diseases on child health through research.